Kidney Infection (cont.)

Siamak N. Nabili, MD, MPH

Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

How is kidney infection diagnosed?

Kidney infection may be diagnosed by a physician by performing a complete physical examination and taking a detailed medical history. The evaluation includes checking the vital signs (heart rate, blood pressure, temperature, and respiratory rate), assessing for signs of dehydration, and checking for tenderness on the mid and lower back. In young, female patients a pelvic exam may also be necessary to evaluate for pelvic infection (pelvic inflammatory disease or PID). A pregnancy test may also be performed.

Urinalysis test is essential for the diagnosis of kidney infection. The urine sample must be properly collected. The urethra needs to be wiped clean properly before the sample is collected in order to avoid contamination of urine by the bacteria on the skin around the urethra. The initial stream of urine is preferably voided in the toilet before the collecting urine in the provided container. This is called the mid-stream, clean-catch urine. After an appropriate amount of urine is collected (about 10 milliliters or cc's) in the container, the remaining urine may also be voided in toilet.

A urinalysis suggestive of an infection in the urine (presence of white blood cells or bacteria in the urine) in general, is highly suggestive and supportive of the diagnosis of kidney infection or urinary tract infection. A urine sample without evidence of urine infection makes kidney infection unlikely and another diagnosis may be considered.

Once white blood cells and other indications of urine infection (such as, leukocyte esterase [produced by white blood cells in urine] or nitrites [produced by bacteria in urine]) are noted on the urinalysis, it is important to determine the amount and the type of bacteria in the urine sample. Generally, a urine sample that has greater than 100,000 bacteria in one cc of urine is considered diagnostic of urinary tract infection. In some clinical settings, counts of less than 100,000 bacteria in one cc of urine may also indicate kidney infection in a clinical setting supportive of this diagnosis.